Control means for heat exchange apparatus



\ Dec. 25, 1951 J.- :E. WOODS CONTROL MEANS FOR HEAT EXCHANGE APPARATUS Filed Feb. 27, 1948 Patented Dec. 25, 1951 CONTROL MEANS FOR HEAT EXCHANGE APPARATUS John E. Woods, Cohasset, Mass., assignor to Standard-Thomson Corporation, Boston, Mass., a corporation of Delaware ApplicationFebruary 27, 1948, Serial No. 11,491

1 Claim.

The present invention relates to heat exchange apparatus and more particularly to heat exchange apparatus of the type described in my copending application Serial No. 514,383, filed December 15, 1943, Patent No. 2,437,287 granted March 9, 1948.

The apparatus shown in said patent comprises an aircraft oil cooler in which eachtube is provided at the rear with an individual temperaturecontrolled closure device. In its preferred form the closure device comprises a biemetallic memher having petal-like leaves which are adapted to close together at low temperatures and to open at higher temperatures. The apparatus is particularly suitable as an oil cooler because the individual devices control the flow through individual tubes and hence serve to promote the rapid thawing at any localized spots where the oil may have congealed.

The objectof the present invention is to provide an apparatus similar in general to that described inflmy co-pending application and having the same advantages but of cheaper and simpler construction.

v To this end and with other objects in view as will hereinafter appear, the principal feature of the invention comprises the use of individual thermostatic units mounted on groups of tubes. Preferably each unit is mounted on a small group covering only a localized portion'of the entire area of the core whereby the apparatus has the advantage of permitting different responses in different sections. Thus if a portion of the core contains congealed oil, the groups of tubes in that region will be closed off from air flow so that rapid thawing in that region is promoted, while cooling 'air is freeto flow'through other groups of tubes which are surrounded by uncongealed oil.

In the accompanying drawings, Fig. l is a view illustrating the manufacture of the thermostatic units; Fig. 2 is a perspective view of a completed unit; Fig. 3 is a face view of a portion of the core of a heat exchanger having units applied thereto in accordance with the present invention; Fig. 4 is a sectional view on line 4--4 of Fig. 3; and Figs. 5 and 6 are views showing a modified form of group thermostat.

As shown in Figs. 3 and 4-. the invention includes a heat exchanger core of the general type described in my Patent No. 2,298,996 comprising a large number of closely-spaced thin wall tubes 6, mounted at opposite ends in a rear header plate 8 and a front header plate (not shown in the drawings). As an example, the core may employ tubes .210" in diameter and about .006" in wall thickness spaced about .250 on centers. The core may have 3,000 or more tubes. The tubes project slightly through the rear header as indicated at I4. The tubes may be suitably bonded to the headers by soldering or brazing as described in my above-mentioned patent.

As is customary in devices of' 'this kind, the entire core is enclosed in a tank or casing having suitable inlet and outlet ports for introducing oil into the spaces between the tubes. The apparatus is placed in the cooling duct of the airplane in such a direction that air flows through the tubes in the direction of the arrow in Fig. 4.

At the rear of the core there are provided thermostatic control members indicated at It, each being associated with a group of tubes. As shown in Fig. 3, each unit It is associated with seven tubes. The seven tubes of each groupform a hexagonal array on which the thermostatic unit may be mounted. Each unit It may be simply slipped over the tube ends and held by frictional engagement, or may bepositively received to one or more tubes, as by soldering or brazing. Each unit is formed from bendable thermostatic bi-metal material. Preferably the units are formed by stamping them out of a sheet of bi-metal as shown in Fig. 1, each member having a tab 11 so that the member may be rolled up and soldered or welded by the tab. As shown in Fig. 1 the member [6 in flat form is provided with a series of leaves or petals i8 of curved shape such as that in the unit of Fig. the petals will close at low temperatures. The device is adapted to fit closely over the six outside tubes of the group. The petals are preferably six in number to close in the manner illustrated in Fig.

It will be observed that the general shape of each unit is hexagonal and the hexago'ns are arranged in such a manner that each petal I8 is adapted to open against a similar petal is of the next adjacent thermostatic member. It will be observed from Fig. 3 that with staggered rows or columns of tubes, the hexagonal units l6 do not necessarily form a true honeycomb, but the petals of adjacent units are disposed in a substantially back-to-back relation.

At low temperatures the control members are closed as shown in Figs. 3 and 4, substantially blocking the air flow except for inconsequential leakage between the petals. In an oil cooler this represents the condition in which the oil is at low temperature so that the air in the tubes 6 is not heated. As the oil thaws out and increases in temperature the air is warmed in its passage through the tubes. The air thus warmed passes over the petals l8 and causes them to open outwardly, thereby opening the passages. The feature whereby each petal of the unit backs up against asimi-lar-petal of the next adjacent unit is important; Itwill be observed that if the air temperature increases above normal hot operating temperature, the petals of adjacent members will engage one another and thus limit the extent of opening movement. But for this feature, the petals of adjacent members under overheating conditions might expandxsufiiciently to block the passage of air throughadja'centzgroups of tubes.

It will also be observed that while the number of thermostatic units is considerably reduced with respect to that shown in my co-pending applica- I tion, the arrangement isisuch that each unit responds only to air temperature within a localized region. Hence the units are capable of responding individually to their own air temperatures, which temperatures are dictated by the condition of the oil in their immediate vicinity. This localized grouping is to be distinguished from arrangements in which the units'might extend across an entire row of tubes, for example, in which case the thermostatic unit. would respond only to the average temperature effects across the whole core.

According, to the present invention, thawing of congealed portions of. the oil is rapidly. promoted while maintaining adequate. cooling in thosesections where the, oilis fluid.

The devices are not limited to groups of seven tubes. The nextlarger group size adaptedto'the hexagonal unit comprises 19 tubes. For a core having a large number of tubes, asufiiciently selective local action may be attained with such larger groups. It will be understood that with some header patterns it may not be possible to fit all tubes at the edges of the core with group thermostatic units, but such tubes may be supplied with individual units of the type shown in my Patent No. 2,437,287.

Hexagonal groupings are not essential. Another embodiment of my invention is shown in Figs. and 6. In that form of the invention a clamshell type of arrangement is used, having nearly flat leaves 22 extending along a number of tubes in a row. The fabricated unit'is indicated at 24; The thermostatic leaves 22 are adapted to close together along an edge 26. The ends of the unit are closed by small petals 28 of a-shape conforming to the closed condition oftheleaves 22, whereby the joining edge 3!] is tightly sealed. The units 24 are applied to a group of tubes at the rear of the oil cooler. Preferably each unit spans four or five tubes of a single row. This provides a sufiiciently localized action whereby as in the device of Figs. 3 and 4, the units will be responsive to the actual temperature conditions existing in the oil at various portions of the unit. As in Fig. 3 the units are in a back-to-back relation, whereby under overheating conditions, no leaf or petal is permittedto curve over any adjacent fluid-flow passage.

The units of Fig. 6 are fabricated from flat bimetal sheets of the general shape of Fig. 5, each having a closing'tab 32 similar to the tab ll of Fig; 1.

It will be understood that although two preferred embodiments of the invention have been described, the invention is not limited to such embodiments but may. be utilized with other arrangements whereby thermostatic members are associated with localized groups of tubes responsive to air flow at the rear of the oil cooler unit. The costof the units andthe-difi'iculty of assembly on the core are greatly reduced with respect to the individual units'shown in my; priorpatent;

Having thus ,described my invention, I claim:

In heat exchange apparatus having. a: large number of tubes for the flow; of a congealable liquid exteriorly and of cooling fiiiid interiorly; apertured tube sheets: in which the tubes are mounted, control units applied to localized small groups of tubes at the rear thereoneach unit being of generally hexagonalcontourrto be received on a group oftubesan'dthavingbendable thermostatic leaves to close the" tubes at low temperatures and to open for substantially unrestricted flow' at higher temperatures, the. sides ofeach unit. engaging thesides' of adjacent units to limit. the movement-at excessive. temperatures, said engagement being only partial along: the sides of the units, whereby. the units; are offset from a true honeycomb relationship.

JOHN E. WOODS.-

REFERENCES CITED" The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date- 1,189,786 Byrnes July 4-, 1916 1,459,318 Birdsall .r June*19, 1923 2,437,287 Woods Mar. 9, 1948 FOREIGN PATENTS Number Country Date 7 554,663 Great Britain: July 14, 1943 554,728 Great Britain July 16,1943 587,421. GreatBritain -rhah. Apr. 24,. 1947 510,960 Germany Oct. 24, 1930 

